CVE-2025-55339: Windows 11 22h2 Privilege Escalation Flaw

CVE-2025-55339 Overview

CVE-2025-55339 is an out-of-bounds read vulnerability in the Windows Network Driver Interface Specification (NDIS) component. An authorized local attacker can exploit the flaw to elevate privileges on affected Windows 11 and Windows Server systems. The weakness is classified under [CWE-125] (Out-of-bounds Read) and requires local access with low privileges. Microsoft published the advisory on October 14, 2025, and released fixes through the standard Patch Tuesday channel. Successful exploitation yields high impact to confidentiality, integrity, and availability, enabling escalation to SYSTEM-level context on the target host.

Critical Impact
A local, authenticated attacker can trigger an out-of-bounds read in the NDIS kernel component to escalate privileges and gain full control of the affected Windows system.

Affected Products

Microsoft Windows 11 (22H2, 23H2, 24H2, 25H2)
Microsoft Windows Server 2022 and Windows Server 2022 23H2
Microsoft Windows Server 2025

Discovery Timeline

2025-10-14 - Microsoft publishes advisory and security update for CVE-2025-55339
2025-10-14 - CVE-2025-55339 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-55339

Vulnerability Analysis

The vulnerability resides in the Windows NDIS kernel-mode component, which brokers communication between network protocol drivers and underlying network adapters. NDIS runs in ring 0, so any memory-safety defect within it directly exposes kernel memory to unprivileged callers. The flaw allows an authorized local process to read memory beyond the bounds of an allocated buffer during NDIS request handling. Kernel memory disclosure can leak pointers, tokens, or object headers that defeat Kernel Address Space Layout Randomization (KASLR) and enable follow-on primitives leading to elevation of privilege.

Root Cause

The underlying weakness is an out-of-bounds read [CWE-125]. Insufficient validation of a length or offset field during processing of a caller-supplied structure causes NDIS to read past the end of a kernel buffer. When combined with attacker-controlled input crafted through IOCTLs or driver interfaces exposed to user mode, the read primitive returns kernel data to the caller or influences control flow in a manner that supports privilege escalation.

Attack Vector

Exploitation requires local access and low-privileged code execution on the target system, with no user interaction. An attacker running as a standard user submits a malformed request through a user-mode interface that ultimately reaches the vulnerable NDIS code path. By chaining the memory disclosure with additional kernel exploitation techniques, the attacker escalates to SYSTEM. This class of bug is commonly used as the second stage of intrusions after initial access through phishing, malicious documents, or compromised software.

No verified proof-of-concept code has been published. See the Microsoft Security Update CVE-2025-55339 advisory for the vendor's technical description and update packages.

Detection Methods for CVE-2025-55339

Indicators of Compromise

Unexpected loading or interaction with NDIS-related drivers (ndis.sys) by non-system processes
Unusual DeviceIoControl calls from standard user processes targeting network driver device objects
New or unsigned services and scheduled tasks appearing shortly after a low-privileged process spawns a SYSTEM-level child
Kernel bug checks or Event ID 41 crashes on hosts running vulnerable NDIS versions

Detection Strategies

Monitor process lineage for privilege transitions from medium or low integrity processes to NT AUTHORITY\SYSTEM without a legitimate elevation path
Alert on suspicious handle acquisition to NDIS device objects (\Device\Ndis, \Device\Nsi) from non-networking binaries
Correlate Sysmon Event ID 1 (process create) and Event ID 10 (process access) with token privilege changes in Security Event ID 4672
Baseline legitimate NDIS-consuming applications and flag deviations

Monitoring Recommendations

Enable Microsoft Defender or equivalent EDR kernel telemetry on all Windows 11 and Windows Server 2022/2025 hosts
Forward Windows Security, Sysmon, and driver load events to a centralized SIEM for cross-host correlation
Track patch compliance for the October 2025 cumulative update across the fleet and alert on missing installations

How to Mitigate CVE-2025-55339

Immediate Actions Required

Apply the October 2025 Microsoft security update referenced in the MSRC advisory to all affected Windows 11 and Windows Server systems
Prioritize patching of multi-user hosts, jump servers, and terminal servers where local access by standard users is expected
Restrict interactive and remote logon rights to trusted administrators until patches are deployed
Audit installed third-party network filter drivers and remove unnecessary components that expose additional NDIS attack surface

Patch Information

Microsoft released fixes for CVE-2025-55339 through the October 14, 2025 security update cycle. Updates are available for Windows 11 versions 22H2, 23H2, 24H2, and 25H2, along with Windows Server 2022, Windows Server 2022 23H2, and Windows Server 2025. Consult the Microsoft Security Update Guide entry for CVE-2025-55339 for KB article numbers matching each supported build.

Workarounds

No official workaround is documented by Microsoft; installing the security update is the supported remediation
Enforce the principle of least privilege and application allowlisting to limit which local users can run untrusted binaries capable of triggering the flaw
Enable Hypervisor-Protected Code Integrity (HVCI) and Credential Guard to raise the cost of chaining kernel read primitives with credential theft

bash

# Verify installation of the October 2025 cumulative update on Windows
Get-HotFix | Sort-Object -Property InstalledOn -Descending | Select-Object -First 10

# Confirm NDIS driver version and signing status
Get-Item C:\Windows\System32\drivers\ndis.sys | Select-Object VersionInfo